Kilt pins originally were exactly that. A large, practical, safety-pin type of thing. That was what you wore with your kilt whether you were a man or a woman. Brooches were decorative items, often jewelled, worn by ladies above the waist. Plaid brooches were large, circular items used to fasten a plaid at the shoulder as a practical necessity to stop it slipping off and are an ancient type of brooch, being found in many archaeological sites. As with all things fashions change and variations on the ladies' brooch theme have found their way into kilt-wearing, perhaps due to a declining popularity among women. These have been suitably masculinised into macho swords etc. to preserve the wearer's gender identity although some, such as a recent post about grouse foot brooches are pushing these boundaries even further. What next you might ask?